The invention relates to an air-sprung vehicle seat wherein a seat frame carrying a seat cushion is supported on a base frame by way of an air spring, and wherein there is a means for adjustment in respect of weight comprising a control cam means and two spaced-apart switch means, one of which switch means controls the supply of air into the air spring and the other controls the discharge of air out of the air spring, and wherein the two switch means are movable relative to the control cam means in dependence on the height of the seat frame from the base frame, and are actuable by the control cam means.
In a air-sprung vehicle seat of this kind, the seat always remains at the same height, irrespective of the weight of the person sitting thereon. If a heavier person sits down on the seat, then the seat moves resiliently downwardly, whereby the switch means for supplying air to the air spring is switched on by way of the control cam means, so that the seat returns to its previous level. Conversely, when a lighter person sits on the seat, the switch for the discharge of air out of the air spring is switched on by way of the control cam means, so that the seat also returns to its previous level.
If the seat is to be held precisely at a given height, then the two switch means must be disposed relatively close together. However, unless further arrangements are made, this has the result that, in operation, when the seat is continuously moving up and down, air is continuously suypplied to and discharged from the air spring, which results in an undesirably high level of air consumption and can also result in critical oscillatory movement.
In order to remedy this disadvantage, DOS (German laid-open application) No 27 53 105 proposes that the control cam means or the switch means may be arranged on a freely displaceable drag or entrainment disc which, when the seat oscillates in both directions, is entrained by a certain distance behind the seat. In this arrangement, a certain degree of friction must be opposed to the movement of the disc so that the disc remains in a rest condition upon deflection of the seat in one direction. On the other hand, the connecting linkage member which entrains the disc after having covered the above-mentioned certain distance and on which the seat frame is guided is arranged closely adjoining the disc and is pivotal about the same axis of rotary movement as the disc so that in operation, and more particularly when the arrangement is suffering from fouling, there is the danger that the disc may be entrained immediately, without a trail effect. This however then also gives rise to the above-indicated disadvantage.